SEMICONDUCTOR LOGIC CIRCUIT

摘要

PURPOSE:To quicken the falling of an output signal by detecting a transient current caused due to parasitic capacitance of a bipolar transistor(TR) caused at the time of rising and providing a TR falling its output signal in response thereto. CONSTITUTION:A transient current Ipass flowing through a parasitic capacitor CCB at the time of rising and only at transient state is detected by a forward internal resistor of a diode 18 and fed to a TR 19. Thus, the TR 19 is turned on, a current Idis flows to the ground and the potential at an output terminal OUT goes immediately to a low level together with a TR 17 turned on simultaneously. Then an output signal is kept low by the ON-state of a 2nd bipolar TR 17 and the ON-state of the MOS TR 15 with a 2nd MOS gate circuit 21 turned on thereby increasing the falling responsiveness considerably. Thus, the transient current flowing uselessly for the charging/discharging of the CCB of a 1st bipolar TR 16 is utilized effectively to improve the performance of the logic circuit.